From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Summary of performance comparisons for narrow brush machines, focusing on output, temperature, and brush angles.
| Identifier | WestWitteringFiles\O\2April1926-June1926\ Scan088 | |
| Date | 13th May 1926 | |
| Contd. -4- EFC/T13.5.26. or it may be due to the increased air gap. It would, of course, have been possible to show a curve taken at a temperature of 75°, in which case the outputs of the two machines would be comparatively similar. In fact, in preparing curves to illustrate the actual output on the chassis where the dynamo temperature may be considered to be, say, 75°C on the average, the curve is usually given at this temperature. In the present case, however, it is desired to bring out the relative differences in the internal heating of the machines. Summarising, these curves show that the narrow brush machine (for the same peak output as set by the control brush) # (1) Maintains the output at high speeds more nearly to the requirements of our specified curve. (2) Requires a 3° smaller angular span for full excitation. (The angle between the main brush and control brush is 125° for these experimental machines, as against 122° for the present standard. The exact position of the main brushes has also been modified in accordance with careful trials for the best general result.) and (3) Runs with a smaller temperature rise. for the same output. The external design of brush holders has not been altered in any way - we have merely obtained brush holders solid and slotted out suitably to take the narrower brushes. EFC. | ||